The raft could test one claim: that a balsa raft could carry people from Peru to Polynesia. The claim it was built to serve, that Polynesia had been settled from South America, could only be tested by other means, and most of those means were already in use before the raft was built. This piece goes through them in order, with what each found, and ends with the finding of 2020 that is the nearest thing to a confirmation Heyerdahl has had, and is not one.

Language, 1846

The United States Exploring Expedition of 1838 to 1842 carried a philologist, Horatio Hale, whose Ethnography and Philology was published in Philadelphia in 1846 as the sixth volume of the expedition’s reports. Its section on the origin of the Polynesians opens: “That the Polynesians belong to the same race as that which peoples the East Indian Islands is, at present, universally admitted. If any doubt had remained on this point, the labors of Wm. Von Humboldt and Professor Buschman, would have been sufficient to set it at rest.” Hale had traced the Polynesian dialects back to Samoa and Tonga and was asking only from which part of the Indonesian archipelago the first settlers of those groups had come. The family that Hale and Humboldt described is now called Austronesian; it stretches from Madagascar to Easter Island, and Polynesian sits inside it as one of its youngest branches.

Heyerdahl’s 1950 paper said that the Polynesian language was “only remotely related to the Malay tongues”. Robert Heine-Geldern’s answer in December 1950 was that even if that were so, “it still would mean that some kind of relation, be it ever so remote, exists between the Polynesian and Indonesian languages, whereas no such link exists between the languages of Polynesia and America.” The one Quechua word in Polynesia, kumara for the sweet potato, “proves that some contacts have taken place between the two regions, but no more.”

Adzes, 1950

Heine-Geldern’s own field was the stone tools of south-east Asia, and this was the part of his criticism that did not depend on argument. “The simple quadrangular adze can be traced from China through Indo-China, the Malay Peninsula and Indonesia to Polynesia, and the stepped and shouldered adzes of eastern Polynesia and Hawaii have their prototypes in the region from the Chinese coast around Hongkong through the Philippines to Celebes.” And then: “Not a single specimen of any of the characteristic South American types of stone axes has ever been found in Polynesia. On the other hand, the various kinds of Polynesian stone adzes all belong to well-known east Asiatic types. Even the way they spread from the Asiatic continent, and while spreading developed, can be traced to some extent. I do not see how the thesis of the American origin of the Polynesians can be reconciled with these facts.”

He also went through Heyerdahl’s list of parallels, megaliths, stepped platforms, the Pleiades calendar, brother-and-sister royal marriage, the sling, the nose flute, and found each of them in Indonesia or on the Asian mainland as well as in Peru. His verdict on the method was that it consisted “in listing various cultural traits found in Polynesia, as well as in America, omitting however to mention that these same traits occur also in Indonesia or eastern Asia.”

Radiocarbon, 2011

Heyerdahl’s first wave was dated, in the despatches of 1947, to “1500 years ago”, and his second to about 1100. The chronology of the islands was then a matter of genealogies and guesswork, and the first radiocarbon dates of the 1950s and after produced a long, loose chronology in which a Peruvian first settlement had room to fit. In 2011 Janet Wilmshurst, Terry Hunt, Carl Lipo and Atholl Anderson went through 1,434 radiocarbon dates from the fifteen archipelagos of East Polynesia, kept only those from short-lived materials that could date an event precisely, and found that the colonisation “occurred in two distinct phases: earliest in the Society Islands A.D. ∼1025-1120, four centuries later than previously assumed; then after 70-265 y, dispersal continued in one major pulse to all remaining islands A.D. ∼1190-1290.” The Marquesas, the Tuamotus, Easter Island, Hawaii and New Zealand were all settled within a century of one another, from the west, and there was no earlier layer for a Peruvian people to have left.

The sweet potato, 1932 to 2018

The sweet potato, Ipomoea batatas, is American. It was growing in Polynesia, under a name that is Quechua, when Europeans arrived, and it was the best single piece of evidence Heyerdahl had. Roland Dixon’s paper of 1932 set out the problem; by 1934, as Heyerdahl noted with regret in 1951, Dixon had concluded that “since we have no evidence that at any time the Indians of the Pacific Coast of South America where the sweet-potato was grown, had either the craft or the skill for making long sea journeys, we are forced to conclude that the transference of the plant was carried out by Polynesians.” The raft’s effect on that argument was the one Heine-Geldern drew: if a raft could go west, a canoe could go east and come back, and the sweet potato could have made the journey either way.

The plant’s own genes have been read twice since. In 2013 Caroline Roullier and her colleagues, using chloroplast and nuclear markers in modern and herbarium samples, found “strong support for prehistoric transfer(s) of sweet potato from South America (Peru-Ecuador region) into Polynesia”. In 2018 Pablo Muñoz-Rodríguez and his colleagues, sequencing whole chloroplasts and 605 nuclear regions from 199 specimens of the sweet potato and its wild relatives, reported “evidence that the sweet potato was present in Polynesia in pre-human times”, which, with other cases of long-distance dispersal in the genus, “negates the need to invoke ancient human-mediated transport as an explanation for its presence in Polynesia.” The two findings are still argued over. A chicken bone from Chile, reported in 2007 as evidence of a Polynesian introduction before Columbus, was challenged in 2008 by a second group who found its DNA consistent with a European origin.

The genomes, 2014 to 2024

In 2014 J. Víctor Moreno-Mayar and his colleagues sequenced genome-wide data from twenty-seven living Rapanui, the people of Easter Island, found “genome-wide patterns consistent with Native American and European admixture”, and dated the American component, from the lengths of the ancestry segments in eight unrelated individuals, to between 1280 and 1495. In 2017 Lars Fehren-Schmitz and his colleagues tested that date directly with five ancient individuals from Ahu Nau Nau at Anakena, from before and after European contact, and could “reject the hypothesis that any of these individuals had substantial Native American ancestry”; the American signal in living islanders, they suggested, “may thus be due to events in more recent history.”

On 8 July 2020 Nature published the paper that changed the question. Alexander Ioannidis, Andrés Moreno-Estrada and thirty colleagues analysed genome-wide variation in 807 people from seventeen island populations across Polynesia and fifteen Native American groups of the Pacific coast. Their abstract: “We find conclusive evidence for prehistoric contact of Polynesian individuals with Native American individuals (around AD 1200) contemporaneous with the settlement of remote Oceania. Our analyses suggest strongly that a single contact event occurred in eastern Polynesia, before the settlement of Rapa Nui, between Polynesian individuals and a Native American group most closely related to the indigenous inhabitants of present-day Colombia.” The signal appeared on the easternmost islands and on no others: the Marquesas, Mangareva, the Palliser atolls of the Tuamotus and Easter Island. The dates estimated island by island were close to one another: Mangareva 1230, Palliser 1230, the North Marquesas 1200, the South Marquesas 1150. The earliest, for Fatu Hiva, was close to the radiocarbon date for the settlement of the Marquesas, “raising the intriguing possibility that upon their arrival Polynesian settlers encountered a small, already established, Native American population.” The authors noted that it is north of Peru, in Ecuador and Colombia, that the coast turns from desert to forest fit for boat-building, that balsa sailing rafts from there are believed to have traded with Mesoamerica between about 600 and 1200, and that drift simulations from that coast “arrive with the highest probability in the South Marquesas islands, followed by the Tuamotu Archipelago”. They did not decide which way the voyage went, and left open that Polynesians, “using their characteristic upwind exploration”, might have found America and come home.

In September 2024 the same journal published fifteen ancient Rapanui genomes, radiocarbon dated to between 1670 and 1950, sequenced by Moreno-Mayar and his colleagues. The individuals “are Polynesian in origin and most closely related to present-day Rapanui”, and “the ancient and present-day Rapanui carry similar proportions of Native American admixture (about 10%)”, which the authors date to “about 1250-1430 CE”. That settles the argument of 2014 and 2017 in favour of a real, pre-European American contribution on Easter Island.

What the tests found

Every test of the second claim came out against it. The languages are Austronesian. The adzes are East Asian. The islands were settled from the west, late and fast, between about 1025 and 1290. The sweet potato may or may not have needed a boat. And the genomes, which Heyerdahl did not live to see read, found that Americans did reach eastern Polynesia, once, around 1200, and left about a tenth of the ancestry of Easter Island and a measurable share of the Marquesas and the Tuamotus. They were few; the people who met them were already Polynesian; they were related to the peoples of Colombia, where the rafts came from, not to the sun-worshippers of the Peruvian desert; and the meeting took place some seven centuries after the date Heyerdahl’s despatches gave. It is a different claim from his. It is also exactly the kind of claim that a raft could never have tested, and that a laboratory in 2020 could.

Sources

• Horatio Hale, Ethnography and Philology, United States Exploring Expedition, vol. 6 (Philadelphia, 1846), p. 194. archive.org
• Robert Heine-Geldern, “Heyerdahl’s Hypothesis of Polynesian Origins: A Criticism,” The Geographical Journal 116 (1950), pp. 183–192. archive.org
• Thor Heyerdahl, “The Voyage of the Raft Kon-Tiki,” The Geographical Journal 115 (1950), pp. 20–41, and “Voyaging Distance and Voyaging Time in Pacific Migration,” The Geographical Journal 117 (1951), pp. 69–77, for Dixon’s words of 1934 as Heyerdahl quoted them. 1950, 1951
• Janet M. Wilmshurst, Terry L. Hunt, Carl P. Lipo and Atholl J. Anderson, “High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia,” PNAS 108 (2011), pp. 1815–1820. doi.org
• Caroline Roullier, Laure Benoit, Doyle B. McKey and Vincent Lebot, “Historical collections reveal patterns of diffusion of sweet potato in Oceania obscured by modern plant movements and recombination,” PNAS 110 (2013), pp. 2205–2210. doi.org
• Pablo Muñoz-Rodríguez and others, “Reconciling Conflicting Phylogenies in the Origin of Sweet Potato and Dispersal to Polynesia,” Current Biology 28 (2018), pp. 1246–1256; behind a paywall, quoted from the abstract. doi.org
• Alice A. Storey and others, “Radiocarbon and DNA evidence for a pre-Columbian introduction of Polynesian chickens to Chile,” PNAS 104 (2007), pp. 10335–10339; Jaime Gongora and others, “Indo-European and Asian origins for Chilean and Pacific chickens revealed by mtDNA,” PNAS 105 (2008), pp. 10308–10313. Storey, Gongora
• J. Víctor Moreno-Mayar and others, “Genome-wide ancestry patterns in Rapanui suggest pre-European admixture with Native Americans,” Current Biology 24 (2014), pp. 2518–2525; Lars Fehren-Schmitz and others, “Genetic Ancestry of Rapanui before and after European Contact,” Current Biology 27 (2017), pp. 3209–3215; both behind paywalls, quoted from their abstracts. 2014, 2017
• Alexander G. Ioannidis and others, “Native American gene flow into Polynesia predating Easter Island settlement,” Nature 583 (2020), pp. 572–577. The abstract is open; the island-by-island dates, the Fatu Hiva sentence, the rafts of Ecuador and Colombia and the drift simulations are from the author manuscript at PubMed Central. doi.org, Europe PMC
• J. Víctor Moreno-Mayar and others, “Ancient Rapanui genomes reveal resilience and pre-European contact with the Americas,” Nature 633 (2024), pp. 389–397; open access. doi.org